Exercise equipment has been fundamentally the same since modern times. Current exercise equipment provides one or both of resistance (i.e. weights, universal gyms, and the like) or positioning (sit up boards, chin up bars, pilates tables, and the like). The resistance is currently provided by physical devices such as weights, rubber bands, springs, step-up gears, friction devices, and the like.
A disadvantage of current exercise equipment is a lack of portability. Any equipment that attempts to provide resistance to the user is difficult to transport or move around by its very nature. A set of weights, for example, are heavy and cumbersome and must be stored in a rack. Because different muscles require different resistance, a range of weights is required for use. This usually requires a dozen or more plates, barbells, dumbbells, etc. This takes up a lot of room in a gym and even more in a home environment. The immovable nature of the weights means that the user must exercise near the weights (typically inside) and prevents the user from perhaps exercising outside or moving freely to other places that could help with variety and motivation.
Similarly, a system that uses springs or rubber bands requires a large device on which to mount them. Such a device is not portable and takes up too much space.
Another disadvantage of current resistance schemes is that once a resistance is selected, the user cannot change the resistance dynamically during exercise. In other words, the user must temporarily stop exercising to increase or decrease the resistance. This prevents optimum results by preventing a user from doing extra repetitions with slightly less resistance.